(a) Technical Field
The present invention relates to a powder paint composition and a method for preparing the same. More particularly, the present invention relates to a powder paint composition prepared by physically attaching metallic particles to a powder resin, thereby providing a single paint composition (“unification type composition”) combining both metallic particles and a powder resin in a single layer. The powder paint composition of the present invention exhibits no separation or aggregation of metallic particles when coated and also provides a significantly improved metallic texture owing to the orientation of the metallic particles.
(b) Background Art
A powder paint refers to a paint in powder form, which includes a synthetic resin involved in film formation, a pigment, etc. as main components and, optionally, is further mixed with a proper curing agent, filler, etc. Such powder paints do not include a solvent, such as an organic solvent, a reactive monomer, water, etc., which is used in a conventional liquid paint composition.
These powder paints exhibit excellent appearance and mechanical/chemical properties. Also, with the advancement in technology, it has become possible to improve the particle size distribution or dispersibility of the powder paint. Further, since it is very convenient to use, the powder paint is widely used in various industrial applications.
Among the various types of powder paints, a pure epoxy resin-based paint has superior corrosion resistance, chemical resistance, water resistance, etc. and is mainly used in applications, such as plumbing, gas pipes, automobile parts, etc., requiring durability. An epoxy polyester resin-based paint is the most widely used powder paint. With relatively well-balanced film properties, it is widely used in various metal furniture, kitchenware, electric home appliances, construction materials, etc. Polyurethane resin-based paints are superior in appearance, processability, fouling resistance, etc. and are commonly used in electric home appliances, or the like.
In addition, a pure polyester resin-based paint, which exhibits superior weather resistance, is used in aluminum chassis, agricultural machinery, vending machines, aluminum wheels, etc.
In automobile parts where a metallic texture is required, such as the aluminum wheels, a powder paint using a polyester resin-based powder resin as a primer, which is then coated with a liquid base component and finished with a powder, is generally used to provide the desired metallic texture.
One example of a powder paint providing metallic texture is described by US Patent Application Publication No. 2003-0194554, which proposes a paint prepared by charging a powder coating composition including a metallic-effect pigment into a mixer and then adding a powdered chromatic pigment to the mixer. Japanese Patent Publication No. 2001-329226 describes another example in which a powder paint composition is obtained by mixing metal flakes having a leafing agent adsorbed on the surface thereof with a thermosetting resin powder, or by bonding metal flakes having a leafing agent adsorbed on the surface thereof to the surface of a thermosetting resin powder.
Further, US Patent Application Publication No. 2005-0182155 proposes a method for obtaining a colored mixture by providing a base powder, providing a stable colorant dispersion and mixing the base powder with the colorant dispersion. Japanese Patent Application Publication No. 2001-139887 proposes a metallic powder coating composition formed by preheating a powder coating material and a metallic pigment covered with a three-dimensionally crosslinked resin having high compatibility with the powder coating material to a temperature higher than the softening point of the powder coating material. This results in fusion of the metallic pigment with the surface and inside of the resin particles of the powder coating material.
The above powder paint compositions include a powder resin for exhibiting a metallic texture mixed with a metallic pigment or metal flakes.
However, since these powder paints require application of two coating layers in addition to a finish coating, the metallic particles exist in a paint phase separated from the powder resin that constitutes the base powder, as schematically shown in FIG. 1. As a result, the metallic particles are oriented randomly in a film formed by coating and curing the paint, the angle of light reflection is random and the paint is limited in its ability to provide an improved metallic texture.
In order to achieve a metallic texture, metallic particles such as aluminum flakes, etc. have to be mixed in the paint. However, the existing powder resin primers for industrial use are not suitable for automobile use because of staining caused by a difficulty in uniform mixing with the metallic particles and because of diffusion of light reflection caused by random orientation of the particles. Still further, it is difficult to obtain a desired the metallic texture with the existing liquid paints.
Further, as the number of coating applications increases, the appearance becomes worse, particularly because of difficulty in handling impurities. However, if layers are omitted, desired properties may not be obtained. For example, if the base layer is simply omitted to reduce the number of processes and reduce production costs, it is difficult to achieve a high-quality metallic texture desired by consumers.
Accordingly, development of a powder paint which can provide a high-quality metallic texture and which can be prepared by a simple process is keenly needed.
Throughout the specification, a number of publications and patent documents are referred to and cited. The disclosure of the cited publications and patent documents is incorporated herein by reference in its entirety to more clearly describe the state of the related art and the present invention.